Certain bulk materials, although they exist in generally fluid form, are "sticky," "muddy," viscous, or coagulant, collectively referred to hereinafter as "agglomerable." One such agglomerable material is synthetic gypsum, which is highly useful in making Portland cement and wallboard. In general terms, gypsum improves the ease of manufacturing and the strength characteristics of the resultant material, whether it be Portland cement or wallboard.
Synthetic gypsum is a lower-cost replacement for naturally occurring gypsum. Such synthetic gypsum is generally produced as a byproduct from other processes which typically include high-temperature combustion. For this reason, the majority of synthetic gypsum produced in the United States is generated from coal-fired electric power generation plants. Scrubbers are utilized in such power generation plants to collect sulfur dioxide emissions generated during the coal firing process. The scrubbers utilize a filter medium material produced from limestone which is high in calcium. As the filter absorbs sulfur dioxide emissions, the filter material chemically transforms to a calcium sulfate material which is compositionally very similar to natural gypsum. Once the filter becomes spent or saturated, it is typically discarded; it is such typically discarded filters which serve as an excellent source of synthetic gypsum.
The primary drawback to utilizing synthetic gypsum has been its agglomerable characteristics. Manufacturing processes generally require the reactive or constituent materials to be evenly and easily conveyed to and from the various manufacturing apparatus involved in the material processing. Unfortunately, agglomerable materials, such as synthetic gypsum, are difficult to feed and meter reliably in such processes. In particular, synthetic gypsum is generally difficult to convey evenly and at the required rates during Portland cement and wallboard manufacturing. In such manufacturing processes, bulk materials are typically stored and dispensed from hoppers or silos. Such hoppers generally have sidewalls which slope symmetrically and inwardly from their upper edges toward the dispensing area or outlet of the hopper. This typical hopper geometry frequently causes "bridging" at or near the outlet of the hopper, which, in turn, stops flow or makes it erratic.
Even when hoppers are associated with mass flow feeders, such devices do not render the flow uniform because it has been found that the material "bridges" or agglomerates before reaching the mass flow feeders, thereby making the flow erratic.
Some hoppers have more complexly-shaped sidewalls which, in vertical cross-section, have either a curvature or a variety of slopes associated with the sidewalls. Such multiple, sloped sidewalls are nonetheless symmetrical in relation to a central, longitudinal axis of the hopper.
Other systems known in the art make use of a vertical sidewall in the hopper and an opposing angled or sloped sidewall. Examples of such structures are shown in U.S. Pat. No. 4,265,065 (Osada), U.S. Pat. No. 2,376,553 (Hombrook), and Ger. Pat. No. 1,23,749 (Harriman). The geometries of these structures render them incapable of dispensing agglomerable materials, as such materials are generally not able to pass through the outlet, and if they do, the flow is erratic and non-uniform.
There is thus a need for a handling system for agglomerable materials which can reliably and uniformly feed and meter from a hopper.